Such supporting frames permit a surgeon to adjust and fix in position a surgical microscope in a predetermined spatial zone without impairing his surgical activity. Preferably, it should be possible for the surgeon to adjust such supporting frames without requiring strength which would hinder his activity. In order to attain the desired mobility of the surgical microscope while requiring only minimum exertion on the part of the surgeon, it is necessary to balance the weight of the surgical microscope by a counterweight.
In the prior art supporting frame of this type described in U.S. Pat. No. 3,891,301, the weight of the surgical microscope is balanced by a pair of exchangeable and axially adjustable weights positioned, respectively, on an intermediate support and on a lever system. Exchanging or assembling and disassembling of weights, however, are not user-friendly and therefore do not meet the requirements expected of modern surgical equipment.
The invention herein provides a supporting frame that is both readily counterbalanced and easy to use.